The present invention relates to 5,6-dialkyl-7-aminotriazolopyrimidines of the formula I
in which the substituents are as defined below:
R1 is C1-C5-alkyl or C1-C10-alkoxy-C1-C10-alkyl,
R2 is C5-C12-alkyl,
where R1 and/or R2 may be substituted by one to three of the following groups:                cyano, nitro, hydroxyl, C3-C6-cycloalkyl, C1-C6-alkylthio or NRaRb;        Ra, Rb are hydrogen or C1-C6-alkyl.        
Moreover, the invention relates to processes for preparing these compounds, to compositions comprising them and to their use for controlling phytopathogenic harmful fungi.